Investigators at the Yale University School of Medicine have long been interested in the biology, physiology, and pathophysiology of the musculoskeletal system. Researchers from a variety of backgrounds, and from multiple academic departments have increasingly become interested in the field. This growth of interested in the musculoskeletal system has fostered increasing numbers of interdisciplinary projects and has created increasing demands on research services related to the physiologic characterization of bone and other musculoskeletal tissues. Thus, as part of the larger Core Center for Musculoskeletal Disease at Yale, a major component will service as a Physiology Core, with three major functioning subunits; Histology and histomorphometry, Biochemical markers of bone turnover, and bone densitometry. These services will be coordinated under the directorship of Dr. Thomas Carpenter, who has had considerable experience with the utilization and interpretation of these techniques. The Histology and histomorphometry subunit will be under the co-supervision of Drs. Roland Baron and Gary Friedlaender, experts in the techniques involved. The subunit provides detailed histologic study of bone, including preparation of undecalcified tissue sections, specialized staining of bone, and histomorphometric analyses assisted by state-of-the-art computer software. These services will be available to Core members at a substantial discount. Increased personnel support provided by the Core to this subunit will accommodate the need for increased overall usage. The Biochemical markers of bone turnover subunit offers state-of-the-art assays for osteocalcin, bone specific alkaline phosphatase, and tartrate resistant acid phosphatase in serum, and urinary excretion of deoxypyridinoline cross-links. These assays will be performed in one laboratory, thereby eliminating the confusion of sample distribution to various laboratories. The subunit will be supervised by Dr. Caren Gundberg, an expert in the biochemical markers of bone turnover. Services will be made available to Core members at a substantial discount. The Bone densitometry subunit offers bone density determinations by peripheral quantitative computed tomography (pQCT), specifically for rodent models of disease. This component is located in the laboratory of Dr. David Ke, at nearby Pfizer Central Research. This facility provides regular use of a rodent bone densitometer, operated by the Core's dedicated personnel. The overall mission of the Core is to provide the above described research services to Core members in a coordinated manner, such that expenses and duplication of effort can be minimized. Furthermore, the physiology Core will provide support for pilot and feasibility studies, foster training of post doctoral fellows, and enable new investigators to explore the musculoskeletal field with the assistance of the most advanced tools and services available.